'Exceptional' heatwave challenges records

Australia's “exceptional” heatwave has produced record-breaking temperatures, with at least six of the first seven days of 2013 among the top 20 hottest days in the past century.

The extreme January heat has prompted the Bureau of Meteorology to issue a special climate statement, with further updates planned as the scorching temperatures continue.

Data for Monday is still to be fully analysed by the weather bureau, but it may be the hottest of the series and could generate a record average maximum beyond the 40.17 degrees reached on December 21, 1972.

Such a result would make it six days in a row when the national average has been above 39 degrees; tomorrow is expected to make it seven. Prior to this series, the longest run of 39 degrees or more was four days, in 1973.

“This event is ongoing with significant records likely to be set,” the bureau statement said. “A particular feature of this heatwave event has been the exceptional spatial extent of high temperatures.”

The final four months of 2012 were the hottest on record for Australia and January is making an early run at adding to the sequence of especially hot weather.

“Australia-wide, and for individual states, we are currently well above average by many degrees,” said Aaron Coutts-Smith, the bureau's NSW manager for climate services.

Sydney is set to cop its first major blast of the searing heat that has grilled much of Australia for the past week, with 43 degrees forecast.

Today's 40-degree prediction for Perth is one sign that any relief for the bulk of central and southern Australia from the current sweltering temperatures will be shortlived.

“We are seeing that re-intensification” of the heat, said Dr Coutts-Smith.

Melbourne, which is expecting 31 degrees today will feel chilly on Wednesday with a maximum of just 20 degrees before the mercury starts climbing back to 37 degrees on Friday, the bureau predicts.

The data for national averages shows the maximum reached 39.2 on January 2, 39.6 on January 3, 39.3 on January 4, 39.3 on January 5 and 39.6 on January 6.

Interestingly, none of the states has broken individual maximum highs, at least in the data until January 6, underscoring how large in size the overall weather pattern is. The weather bureau's manager for climate monitoring, Karl Braganza on Monday described the event as a "dome of heat" over the continent.

NSW, which is likely to endure extreme temperatures today, has to exceed 44.1 degrees on average to beat the record set on January 14, 1939. This year, the hottest day was on January 5 when maximums averaged 41.1 degrees, with Hay Airport hitting 47.9 degrees, according to data up until January 6.

For Victoria, the hottest day on record was 44.5 degrees on Black Saturday, February 7, 2009, when bushfires left 173 people dead. In the current spate of heat, the hottest day was January 4 when temperatures across the state averaged 41.2 degrees.

Up until January 6, Yarrawonga had posted the hottest temperature in the state at 45.7 degrees on January 5, while Portland's 42.1 on the previous day was a new daily maximum for that location, the bureau said.

Nationwide, the hottest single temperature recorded during the heat - up to January 6 - has been the 48.6 degrees reached at Red Rocks Point in WA on Jauary 3. That's about 2 degrees below the 50.7 degrees all-time record set on January 2, 1960.